Skip to content

Latest commit

 

History

History
76 lines (59 loc) · 4.16 KB

22 - Day 33 - IPv6 Part 3.md

File metadata and controls

76 lines (59 loc) · 4.16 KB

Day 33 - IPv6 Part 3

Reviewed: No

1. Introduction to IPv6 Static Routing:

  • Focus on Exam Topic:
    • 3.3: Applying IPv4 static routing concepts to IPv6.
  • IPv6 in CCNA:
    • Many students feel less confident with IPv6 because most courses focus primarily on IPv4. Spending more time on IPv6 will build confidence.

2. IPv6 Address Representation Correction:

  • RFC 5952: Standardizes IPv6 address text representation.
    • Leading 0s MUST be removed.
    • Double colon (::) MUST be used to shorten the longest string of all-0 quartets.
    • Hexadecimal letters (a-f) MUST be in lower-case.

3. IPv6 Header Overview:

  • IPv6 Header Simplification:
    • Fixed header size: 40 bytes, making processing easier for routers compared to the variable IPv4 header (20-60 bytes).
  • Fields in IPv6 Header:
    • Version (4 bits): Indicates IP version 6 (binary 0110).
    • Traffic Class (8 bits): Used for Quality of Service (QoS).
    • Flow Label (20 bits): Identifies traffic flows (e.g., between a server and a client).
    • Payload Length (16 bits): Indicates the length of the encapsulated Layer 4 segment.
    • Next Header (8 bits): Indicates the type of the next header (e.g., TCP or UDP).
    • Hop Limit (8 bits): Similar to IPv4’s TTL, decrements by 1 at each hop; packet discarded when it reaches 0.
    • Source and Destination Address (128 bits each): Contains the IPv6 addresses of the source and destination.

4. Neighbor Discovery Protocol (NDP):

  • NDP Functions:
    • Replaces ARP in IPv6, using ICMPv6 messages instead of broadcasts.
  • Solicited-Node Multicast Address:
    • Formed by combining ff02::1:ff with the last 6 hex digits of the unicast address.
  • Key NDP Messages:
    • Neighbor Solicitation (NS) - ICMPv6 Type 135: Equivalent to ARP request, asks for a MAC address.
    • Neighbor Advertisement (NA) - ICMPv6 Type 136: Equivalent to ARP reply, provides a MAC address.
    • Router Solicitation (RS) - ICMPv6 Type 133: Hosts send to discover routers on the local link.
    • Router Advertisement (RA) - ICMPv6 Type 134: Routers respond to RS messages, announcing their presence.
  • Command to use instead of ARP table: show ipv6 neighbor

5. Stateless Address Auto-configuration (SLAAC):

  • SLAAC Overview:
    • Allows hosts to automatically configure an IPv6 address without manual configuration.
    • Uses RS and RA messages to learn the IPv6 prefix and generate an address (e.g., ipv6 address autoconfig on Cisco routers).
  • Duplicate Address Detection (DAD):
    • Ensures the uniqueness of an IPv6 address on a network by sending an NS to the address itself. If no NA reply is received, the address is considered unique.

6. IPv6 Static Routing:

  • IPv6 Static Route Command Structure:

    ipv6 route [destination]/[prefix-length] {next-hop-address | exit-interface} [AD]

    • Directly Attached Route: Specifies only the exit interface.
    • Recursive Route: Specifies only the next-hop address.
    • Fully Specified Route: Specifies both the exit interface and next-hop address.

  • Types of IPv6 Static Routes:

    • Network Route: Route to a specific subnet.
    • Host Route: Route to a single specific host (e.g., /128 prefix length).
    • Default Route: Route for all destinations not in the routing table (::/0 in IPv6).
    • Floating Static Route: Backup route with a higher administrative distance (AD).

  • Important Considerations:

    • Directly Attached Routes: Cannot be used on Ethernet interfaces in IPv6, unlike IPv4. Must use recursive or fully specified routes instead.

7. Summary and Review:

  • IPv6 Address Representation: Follow the rules from RFC 5952 (e.g., remove leading zeros, use lower-case).
  • IPv6 Header: Fixed 40-byte header simplifies processing.
  • NDP: Replaces ARP, uses multicast instead of broadcast for efficiency.
  • SLAAC: Enables automatic IPv6 address configuration.
  • Static Routes in IPv6: Similar to IPv4 but with key differences, such as the inability to use directly attached routes on Ethernet interfaces.